Radiographic measurements of C-2 in patients with atlas assimilation

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>The object of this study was to evaluate the radiographic characteristics of C-2 using multiplanar CT measurements for anchor screw placement in patients with C-1 assimilation (C1A). Insertion of a C-2 pedicle screw in the setting of C1A is relatively difficult and technically demanding, and there has been no report about the optimal sizes of the pedicles and laminae of C-2 for screw placement in C1A.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>An institutional database was searched for all patients who had undergone cervical CT scanning and cervical spine surgery between April 2006 and December 2012. Two neurosurgeons reviewed the CT scans from 462 patients who met these criteria, looking for C1A and other anomalies of the craniocervical junction such as high-riding vertebral artery (VA), basilar invagination, and VA anomaly. The routine axial images were reloaded on a workstation, and reconstruction CT images were used to measure parameters: the minimum width of bilateral pedicles and laminae and the length of bilateral laminae of the atlas.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Seven patients with C1A were identified, and 14 sex-matched patients without C1A were randomly selected from the same database as a control group. The mean minimum pedicle width was 5.21 mm in patients with C1A and 7.17 mm in those without. The mean minimum laminae width was 5.29 mm in patients with C1A and 6.53 mm in controls. The mean minimum pedicle and laminae widths were statistically significantly smaller in the patients with C1A (p &lt; 0.05).</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>In patients with C1A, the C-2 bony structures are significantly smaller than normal, making C-2 pedicle screw or translaminar screw placement more difficult.</jats:p></jats:sec>

Feasibility of C2 Vertebra Screws Placement in Patient With Occipitalization of Atlas

“…Our measurements showed that the mean C2 pedicle thickness in OA was 3.5 mm and significantly smaller than in the control group (mean 6.4 mm), and also less than that in the Aoyama et al 32 study (mean 5.2 mm). Smith et al 33 reported the mean pedicle thickness was 5.8 mm in normal people, which was close to the value in our study and yet far smaller than that in the Aoyama et al 32 result (mean 7.2 mm). With pedicle thickness of 4 mm, approximately 13.7% of patients may receive pedicle screw fixation at C2 (Table 3 ).…”

“… 33 , 34 Based on this requirement, the percentages dropped to only 1.4% of our patients who may receive pedicle screw fixation at C2 levels. According to Aoyama et al 32 results, there were no pedicle thickness less than 5 mm in the right side, and yet in our study 87.7% and 93.2% of pedicle thicknesses in the right and left side, respectively, were smaller than 5 mm. Smith et at 33 demonstrated the mean pedicle angle was 43.9°, which was close to the normal population (mean 39.5°) and bigger the angle in the patients with OA (mean 36.9°) in our study.…”

“…This pathological condition necessitate the screw placement should be more cautious than usual to avoid VA injury. Aoyama et al 32 reported that there were no laminar thicknesses less than 3.5 mm and even 4.0 mm in the patients group. This finding was not supported by our study because there were 87.7% and 79.5% of the laminar thicknesses bigger than 3.5 and 4.0 mm, respectively, although the mean laminar thicknesses were similar in both studies.…”

“…In 2014, Aoyama et al 32 evaluate the radiographic measurement of C2 pedicles and laminas using multiplanar CT measurements for anchor screw placement in patients with C1 assimilation. This report included only 7 patients, whereas that of the present study included 73 patients.…”

“…This report included only 7 patients, whereas that of the present study included 73 patients. Moreover, we analyzed the length and angle of the pedicle, lamina, and lateral mass of C2, which was not done in the Aoyama et al 32 study.…”